A randomized controlled trial of a "Small Changes" behavioral weight loss treatment delivered in cardiac rehabilitation for patients with atrial fibrillation and obesity: study protocol for the BE-WEL in CR-AF study.

Background: Atrial fibrillation (AF) represents a global epidemic. Although international AF practice guidelines indicate weight loss for patients with AF and comorbid obesity (BMI ≥ 30 kg/m) to alleviate symptom burden and improve prognosis, few cardiac rehabilitation (CR) programs include targeted weight loss treatment.

Aims: This RCT protocol will evaluate the efficacy of a "Small Changes" behavioral weight loss treatment (BWLT) to produce clinically relevant (≥ 10%) weight loss among patients with AF and obesity undergoing CR, relative to CR alone. Secondary aims are to establish efficacy of CR + BWLT for improving AF symptoms, AF risk factors, and health-related quality of life.

Methods: Adults (18 +) with AF and obesity will be recruited and randomized to receive CR + BWLT (intervention) or CR-only (control). Controls will receive CR consisting of supervised exercise and risk factor self-management for 12 weeks. The intervention group will receive CR plus BWLT (12 weekly, group-based virtual sessions, followed by 12 weeks of follow-up support). Weight and AF-risk factors will be assessed at pre-randomization, 12 weeks, 24 weeks, and 52 weeks. AF burden will be assessed using 30-s ECGs recorded bidaily and with AF symptoms. The primary endpoint of weight loss will be calculated from baseline to 52 weeks as a percentage of starting weight. Intention-to-treat analyses will compare the proportion in each group achieving ≥ 10% weight loss. Assuming success rates of 5% and 30% among controls and intervention groups, respectively, and a 30% loss to follow-up, 120 patients (60 per group) will provide 80% power to detect a difference using a two-sided independent test of proportions (alpha = 5%).

Impact: This clinical trial will be the first to demonstrate that adding BWLT to CR promotes clinically meaningful weight loss among patients with AF and comorbid obesity. Findings will inform design and execution of a large efficacy trial of long-term (e.g., 5-year) clinical endpoints (e.g., AF severity, mortality). Implementing weight control interventions designed to target the AF substrate in CR could dramatically reduce morbidity and enhance quality of life among patients living with AF in Canada.

Trial Registration: ClinicalTrials.gov registration number: NCT05600829. Registered October 31, 2022.